摘要:

AbstractUncemented total hip replacements have resulted in a higher incidence of postoperative complaints than cemented ones. The theoretical explanation of these not well defined discomforts is based on the differences of the stress and strain fields around the distal portions of the femoral components. While the noncemented stems are press‐fitted and most of them tapered distally, thus creating hoop stresses and strains in the surrounding cortical bone, the shrinkage of the cement prevents these mechanical irritations. The relatively sudden disappearance of these discomforts within the first 2 postoperative years is attributed to the shift of the main zone of load transmission from the distal to the proximal portion of the stems following bone remodelin

ISSN:0021-9304    

DOI:10.1002/jbm.820230702

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractCreation of life involves establishing an organism that is capable of self‐maintenance, self‐reproduction, and adjustment to a changing environment. A Bioactive Substrate Theory of the origin of life is proposed, where the function of the bioactive substrates was to achieve the irreversible ordering of macromolecules into replicative structures. The ordering was a result of six precytic ordering factors which provide the mechanisms for simultaneous formation of primitive codonic‐bases, anabolic processes and energy‐producing, catabolic processes on bioactive inorganic glassy crystalline assemblages. Time dependent changes in the isoelectric point of the inorganic assemblages enabled the anabolic and catabolic processes to be isolated within the same bilipid membrane. The enormous diversity of inorganic glass‐crystal assemblages associated with volcanic activity resulted in many alternative evolutionary pathways for the precytic structures, eventually producing the major genetic pathways for life observed today. The evidence for bioactive ordering factors is examined including selective adsorption of optically active amino acids on optically active mineral substrates and specific cellular responses to bioactive implant materials. The implications of this theory on the biochemical design of implants, and prevention of disease states in modern man are

ISSN:0021-9304    

DOI:10.1002/jbm.820230703

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe peritoneal cavity is a convenient site for implantation of encapsulated hormonesecreting tissue. However, host tissue organization around such implants may affect solute exchange and viability of the encapsulated tissue. The reaction to polyvinyl chloride acrylic copolymer capsules implanted in the peritoneal cavity of rats and mice was therefore studied. Some animals received a slow release dexamethasone pellet, others were pretreated with doxorubicin, in an attempt to minimize the tissue reaction. The tissue reaction was significantly thicker in rats than in mice at both 2 and 6 weeks after implantation. In rats, corticoids decreased significantly the thickness of the reactive layer as compared to control at all time points studied, but doxorubicin had no effect. The tissue reaction in mice was not significantly affected by corticoid treatment. In both species the thickness of the tissue reaction did not increase significantly between 2 and 6 weeks. At 3 days the tissue reaction consisted of an interrupted single layer of macrophages in mice, whereas in rats the reaction consisted of two or three layers of macrophages and polymorphonuclear cells. At both 2 and 6 weeks, several cell layers surrounded the implants: a single layer of macrophages lying along the polymer, a variable number of layers of fibroblasts interspresed with collagen fibrils (fewer in mice than in rats, and fewer in corticoid treated rats than control rats) and an outer monolayer of mesothelial cells. We conclude that the intensity of tissue reaction to polymer implants in the peritoneal cavity is species dependent and can be decreased by the administration of corticoids but not doxorubicin.

ISSN:0021-9304    

DOI:10.1002/jbm.820230704

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe influence of type and quantity of five different crosslinking agents on tensile creep properties of multiphase acrylic systems has been studied. The polymeric materials, commonly applied in bioengineering, were processed by polymerization of a mixture of liquid methacrylate monomers and poly(methyl methacrylate) powder. The specimens were made with various ratios of methyl methacrylate and crosslinking agents in the monomer liquid. Two different processing conditions were used, i.e., heat‐polymerization at 100°C and autopolymerization at 45°C. Creep behavior was determined at 37 ± 0.2°C and 50 ± 0.5°C. The investigation showed higher creep values for autopolymerized than for heat‐polymerized materials. In heat‐polymerized materials the creep curves showed little variation with type and quantity of crosslinking agents at low stress levels. However, at high stress levels the creep values decreased with increasing quantity of crosslinking agents. The autopolymerized materials showed a more inhomogeneous structure, and great variation in creep. Both among the heat‐polymerized and autopolymerized materials, the systems with diethyleneglycol dimethacrylate clearly deviated from the others by showing higher

ISSN:0021-9304    

DOI:10.1002/jbm.820230705

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractBioactive glass can form an effective bond with bone. Essential for this connection are the interfacial reactions which lead to the development of a Si‐rich film covered by a CaP‐rich film. The presence of these layers can be demonstrated clearly by EDX analysis of fiber‐reinforced bioactive glass and bulk bioactive glass implants installed for 4 and 16 months in the partial edentulous jaws of beagle dogs. EDX analysis reveals three types of microchemical interface. The first type develops when the implant is bonded to bone. Here, a smooth transition of the CaP profile can be observed between bioactive glass and the bone, thus providing for a compositional gradient between the implant and the surrounding tissues. The second type is seen when the implant surface is surrounded by fibrous tissue. This causes a discontinuity in the CaP profile. The third type is characterized by a gradual decrease in the Ca and P concentrations across the interface, caused by the presence of Ca and P in the fibrous tissue near the implant surface. This suggests that the interface is dynamic in time and transforms to a functionally better optimized interface. EDX analysis does not reveal any metal fiber ion contamination of the outer glass rim of the implant. When stainless‐steel or wrought Co‐Cr alloy is exposed to the surrounding fluids, the interfacial osteogenesis is disturbed, possibly by a synergistic effect of glass ions and metal ions. Exposure of titanium does not interfere with this osteogenesis. The bone bonding can also be influenced by surgical trauma. However, with precise implantation techniques, an enhancement of bone growth by osteoconductivity can be

ISSN:0021-9304    

DOI:10.1002/jbm.820230706

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe adhesive properties of a series of oligomers prepared from 2‐isocyanatoethyl methacrylates (IEM) and/orm‐iso‐propenyl‐α,α‐dimethylbenzyl isocyanate (TMI) and various acrylates or methacrylates were studied. The bond strength of bone, dentin, or soft tissue specimens joined with these oligomers respectively to bone, dental composite restorative, or denture base resin were determined by tensile adhesion or shear tests. These oligomers are more effective in forming stronger bonds to bone than are other tissue adhesives. Fracture occurs cohesively, usually within the bone. Thermocycling in water for 1 week between 5°C and 55°C did not decrease adhesion indicating that exposure to water or thermal shock produced no deterioration of the bond. Tensile adhesion of bovine or human dentin joined to composite restorative resin by means of the oligomers is similar to that of the best dental bonding agents such as Gluma (glutaraldehyde and 2‐hydroxyethyl methacrylate) or ferric oxalate + Nphenylglycine + dimethylacryloxyethyl‐pyromellitate. These oligomers also strongly bond soft tissues and calfskin and to acrylic resi

ISSN:0021-9304    

DOI:10.1002/jbm.820230707

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractPrevious studies showed that natural coral implanted into bone tissue was gradually resorbed and progressively replaced by newly formed bone. The objectives of this study were to compare the fate of two Madreporian corals,PoritesandAcropora, after implantation during 1 and 2 months into sheep and pig long bones. These materials are identical in composition (CaCo3) but differ in volume (49 ± 2%, 12 ± 4%, respectively) and mean size (250 vs. 500 μm) of porosities. The non‐decalcified histological slices were observed under light microscopy. Implant resorption and new bone formation were quantified through an automatic image analysis system. Quantitative results showed that the larger the porosity volume, the greater was the coral resorption as well as the new bone apposition. Large differences were found between the two animal species. Histological findings were identical to those previously reported: implants were resorbed and progressively replaced by newly formed bone. Coral was found to be an osteoconductive biomaterial which acted as a scaffold for a direct osteoblastic apposition and consequently could be an interesting alternative to bone auto‐, allo‐, or xe

ISSN:0021-9304    

DOI:10.1002/jbm.820230708

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThree different granule coatings (a granular alumina ceramic coating, a granular hydroxyapatite coating, and a polished granular hydroxyapatite coating) applied to alumina ceramic substrate were evaluated for their strengthening effects of the bone—implant interface in rabbit tibiae. For a comparison, noncoated alumina ceramics, and dense hydroxyapatite were assessed in the same way. The granular alumina ceramic coating, creating a bioinert, porous surface, was effective due to a strong mechanical bond between the bone and implant. The interface strength was even higher than that of the dense hydroxyapatite. The granular hydroxyapatite coating, creating a bioactive, porous surface, was less effective than the granular alumina ceramic coating because of the brittleness of the hydroxyapatite granules, although it formed a direct and mechanical bond with bone tissue. The polished granular hydroxyapatite coating, creating a bioactive, smooth surface, was least effective because of the brittleness of the hydroxyapatite granules, though it presented an improved interface strength compared with that of the noncoated alumina ceramics due to a direct bond between the bone and hydroxyapatite granule

ISSN:0021-9304    

DOI:10.1002/jbm.820230709

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820230710

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820230701

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY